When her grandmother dies, Gabby discovers an old letter concealed in a secret compartment in the roll-top desk made four generations earlier. The secrets it reveals belong to an even earlier generation—the first members of Gabby's family to cross the ocean from Britain to Australia, over 150 years ago.
In 1855 Sarah and Mary are alone on The Colchester, after their parents are both killed by the deadly disease on-board. The family left their home in Wales in an attempt to find a better life in the colonies but with both parents dead the sisters are devastated, with no idea what to do next.
Sarah also becomes ill and, worried about passing her illness to Mary, encourages her to spend the days away from the stuffy cabin, in the fresh air on deck. Befriended by a gentleman, Mary finds herself swept up in a hopeless cycle of shame and lies, with no way out. When the girls arrive in Melbourne they have little hope of finding suitable work and make a drastic decision which could lead either to fortune or disaster.